C. F. Keil and Franz Delitzsch on 2 Chronicles 29:35

2Ch 29:35 2Ch 29:35 gives yet another reason why the Levites had to help the priests: “And also the burnt-offerings were in abundance, with the fat of the peace-offerings, and the drink-offerings for every burnt-offering.” The priests could not accomplish the flaying for this reason also, that they had, besides, to see to the proper altar service (sprinkling of the blood, and burning of the sacrifices upon the altar), which taxed their strength, since, besides the consecratory burnt-offerings, there were the voluntary burnt-offerings (2Ch 29:31), which were offered along with the thank-offerings and the drink-offerings, which belonged to the burnt-offerings of Num 15:1-15. Thus the service of the house of Jahve was arranged. עבודה is not the purification and dedication of the temple (Berth.), but only the sacrificial service, or rather all that concerned the regular temple worship, which had decayed under Ahaz, and had at length wholly ceased.